Method for monitoring performance of network using IP measurement protocol packets

ABSTRACT

The practice and need for active network measurement is well established, however, current tools are not well suited to this task, mostly because the protocols which they employ have not been designed for measurement of the modem Internet. The IP Measurement Protocol (IPMP) is based on packet-probes, and is designed to allow routers to participate in measurements by the insertion of path information as the probe passes between a pair of hosts.

STATEMENT OF RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalPatent Application No. 60/421,303, filed Oct. 25, 2002, entitled “IPMeasurement Protocol.”

This application is also related to copending U.S. patent applicationSer. No. 10/648,724, entitled “Method And Apparatus For Testing An IPNetwork,” filed concurrently herewith by the same inventor and assignedto the same assignee, which application is hereby incorporated byreference as if repeated herein in its entirety, including the drawings.

This application is also related to copending U.S. patent applicationSer. No. 10/648,622, entitled “Method For Performing Remote Testing OfNetwork Using IP Measurement Protocol Packets,” filed concurrentlyherewith by the same inventor and assigned to the same assignee, whichapplication is hereby incorporated by reference as if repeated herein inits entirety, including the drawings.

This application is also related to copending U.S. patent applicationSer. No. 10/648,690, entitled “Method For Enabling Initiation Of TestingOf Network Using IP Measurement Protocol Packets,” filed concurrentlyherewith by same inventor and assigned to the same assignee, whichapplication is hereby incorporated by reference as if repeated herein inits entirety, including the drawings.

This application is also related to copending U.S. patent applicationSer. No. 10/648,682, entitled “Method For Converting An IP MeasurementProtocol To A Data Packet,” filed concurrently herewith by the sameinventor and assigned to the same assignee, which application is herebyincorporated by reference as if repeated herein in its entirety,including the drawings.

This application is also related to copending U.S. patent applicationSer. No. 10/648,549, entitled “Method For Enabling Non-PredeterminedTesting Of Network Using IP Measurement Protocol Packets,” filedconcurrently herewith by the same inventor and assigned to the sameassignee, which application is hereby incorporated by reference as ifrepeated herein in its entirety, including the drawings.

This application is also related to copending U.S. patent applicationSer. No. 10/648,866, entitled “Method For Using Different Packet TypeAnd Port Options Values In An IP Measurement Protocol Packet From ThoseUsed To Process The Packet,” filed concurrently herewith by the sameinventor and assigned to the same assignee, which application is herebyincorporated by reference as if repeated herein in its entirety,including the drawings.

This application is also related to copending U.S. patent applicationSer. No. 10/694,632, entitled “Use Of Synchronized Clocks To ProvideInput And Output Time Stamps For Performance Measurement Of TrafficWithin A Communications System,” filed Oct. 27, 2003 by at least one ofthe same inventors and assigned to the same assignee, which applicationis hereby incorporated by reference as if repeated herein in itsentirety, including the drawings.

FIELD OF THE INVENTION

The present invention is directed to methods and apparatuses fortransmitting packet data over computer networks, and more particularlyto a method and apparatus for transmitting packet data over a publiccomputer network using Internet Protocol, as well as monitoring andtesting these computer networks.

BACKGROUND

A previous method for sending test packets over a computer network wasmostly designed for use in an academic setting. As such, this method didnot provide for centralized monitoring and did not provide mechanisms tosupport use in a commercial environment. An Existing Internet ProtocolMeasurement Protocol (IPMP) involved having hosts and routers placetimestamps in packets as they were forwarded, but did not provide asufficiently rich set of methods for controlling the recording oftimestamps or for providing information about the timestamps that wouldbe needed in a commercial network.

The present invention is therefore directed to the problem of developinga method and apparatus for enabling routers and other network devices toprovide measurement information to permit proper characterization of acomputer network.

SUMMARY OF THE INVENTION

The present invention solves these and other problems by providing interalia a method for monitoring propagation delays and other properties ofpaths in Internet Protocol (IP) networks. One embodiment of this methodincludes an Internet Protocol Measurement Protocol (IPMP) as augmentedand revised herein.

One exemplary embodiment of the IP Measurement Protocol (IPMP) of thepresent invention provides several powerful capabilities, including:

-   1. Redirection capability, which provides the capability to send a    packet from a central location to a second host, and have that    second host re-direct or transmit a measurement packet to a third    host, receive the reply packet and forward the result to the first    host.-   2. A Start Time to Live capability, which prevents measurements from    being taken until the Time to Live (TTL) counter reaches a certain    value, which allows for measurement of very long paths or use of    very short packets, in which it is not possible to fit all the    measurement records into a single measurement packet.-   3. The Information Request Proxy, which allows assignment of certain    information request tasks to a third party. The original IPMP    required that Information Request packets (which were used to get    additional information) had to be sent to the same location that    inserted the measurement records. Many ISPs might not want users    talking to their routers (or some devices may not have addressable    IP addresses as they share a common IP address with one or more    other devices, or exist behind firewalls, etc.) so this aspect of    the present invention provides for designation of an Information    Proxy that can respond for such devices, and the ability to place    the proxy's address along with the routers address into the    timestamp.-   4. Timestamp qualifying information capability in the timestamp. The    present invention provides additional information about how and    where the timestamp was inserted, along with information about the    clock source to allow the timestamp to be used without having to    make any Information Requests. This capability makes the IPMP more    useful for certain applications and protocols that do not need to    send extra messages to be able to use the results.-   5. No timestamp mode capability, which allows for simply collecting    IP addresses without timestamps, e.g., allows the IPMP to be used in    place of Traceroute (http://www.freesoft.org/CIE/Topics/54.htm,    http://www.nwfusion.com/archive/1999b/0712gearhead.html ) as a more    efficient way of finding out of about the path between two points.

According to another aspect of the present invention, while theembodiments of the various inventions herein are described for InternetProtocol version 4 (IPv4), the embodiments of the various inventionsherein are equally applicable to Internet Protocol version 6 (IPv6),which has a different format for the packet header. The same may be truefor subsequent versions of Internet Protocol as well.

According to another aspect of the present invention, one embodiment ofthe IP Measurement Protocol provides that a regular data packet bereplaced with an IPMP packet, which includes in one of the data sectionsextensions the data that would have been in the regular protocol packet,plus a flag that says “take this data out and process this data as ifthis data had been the only contents of a non-IPMP packet, where thefaux ports and packet type were the real ports and packet type.” Assuch, a router or other similar device would then process the packetaccordingly.

According to still another aspect of the present invention, oneembodiment of the IP Measurement Protocol provides that instead of usinga different packet type, the protocol may be carried in InternetProtocol version six (IPv6) header extensions. This embodiment takesadvantage of certain provisions in IPv6 for inserting optional featuresinto “header extensions” between the header and the data portion of thepacket.

According to yet another aspect of the present invention, one embodimentof an IP Measurement Protocol provides a more explicit method ofrequesting information from routers along a path traversed by a packetrather than a single flag that says: “give me everything.” According tothis embodiment, the protocol provides a larger field, or extendablefield, that permits one to request particular information itemsexplicitly.

Other aspects of the present invention will be apparent to thosereviewing the following drawings in light of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an exemplary embodiment of a method for performing ameasurement of a remote host by using an Internet Protocol MeasurementProtocol (IPMP) packet according to one aspect of the present invention.

FIG. 2 depicts an exemplary embodiment of a method for responding to anIPMP redirection request packet sent from a measurement host accordingto another aspect of the present invention.

FIG. 3 depicts an exemplary embodiment of a method for constructing anIPMP echo request packet as part of a response to an IPMP redirectionrequest packet from a measurement host according to yet another aspectof the present invention.

FIG. 4 depicts an exemplary embodiment of a method for responding to anIPMP echo reply packet sent in response to an IPMP echo request packet,which itself was created as a result of an IPMP redirection requestpacket from a measurement host, according to still another aspect of thepresent invention.

FIG. 5 depicts an exemplary embodiment of a method for responding to anIPMP echo request packet, which itself was created as a result of anIPMP redirection request packet from a measurement host, according toyet another aspect of the present invention.

FIG. 6 shows an exemplary embodiment of a process for employing packetssent using the Internet Measurement Protocol of the present inventionfor measuring performance of particular links in a network according tostill another aspect of the present invention.

FIG. 7 shows an exemplary embodiment of a method for performing a remotetest of a link between a first remote network device and a second remotenetwork device by a measurement host according to still another aspectof the present invention.

FIG. 8 shows another exemplary embodiment of a method for performing aremote test of a link between two remote network devices from ameasurement host device according to yet another aspect of the presentinvention.

FIG. 9 shows an exemplary embodiment of a method for using the StartTime to Live capability according to yet another aspect of the presentinvention.

FIG. 10 shows an exemplary embodiment of a process for using the IPMeasurement Protocol to transmit regular data packets according to stillanother aspect of the present invention.

FIG. 11 shows an exemplary embodiment of a method for creating an IPMPpacket with a faux port according to yet another aspect of the presentinvention.

FIG. 12 shows an exemplary embodiment of an apparatus for sending andreceiving Internet Protocol Measurement Protocol (IPMP) packets formeasuring performance of various links in a computer network, such as alink between a first remote network device and a second remote networkdevice, according to still another aspect of the present invention.

DETAILED DESCRIPTION

It is worthy to note that any reference herein to “one embodiment” or“an embodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention. The appearances of thephrase “in one embodiment” in various places in the specification arenot necessarily all referring to the same embodiment.

One application of the present invention is for performance measurementof traffic through the Motorola Broadband Service Router (BSR) 64000.

The present invention can be used to demonstrate to Multiple SystemOperators (MSOs) that BSR delivers promised Quality of Service (QoS)guarantees. MSOs can use to show to subscribers that the MSOs networkhas delivered promised QoS guarantees. This capability allows a hardwaredeveloper and its customers to prove they are delivering advancedservices, not just making marketing claims.

One additional capability includes the ability to redirect the packetmultiple times, for example, to be able to send it out through afirewall and have the packet or echo come back through the firewall.FIG. 12 shows an exemplary embodiment 120 of an apparatus for sendingand receiving Internet Protocol Measurement Protocol (IPMP) packets formeasuring performance of various links in a computer network, such as alink between a first remote network device 123 and a second remotenetwork device 126. The measurement host 121 sends an IPMP packet to thefirst remote network device 123 via network A 122. The first networkdevice in turn sends an IPMP packet to the second remote network device126 via network B 124. The second remote network device 126 may bebehind a firewall 125 or a network address translation device.

A measurement host 121 includes at least a processor and a memory. Theprocessor prepares the IPMP packets as described above and forwards themto remote devices over a first network 122, of which remote devices theprocessor is attempting to determine the performance.

Furthermore, the present invention includes a computer readable mediahaving instructions encoded thereon to cause a network device, such as aserver, router, hub, terminal, or processor to perform the methods andprocesses described herein.

Another additional feature adds security option fields for allowing theIPMP packets to pass through firewalls by putting in a security optionthat the firewall could use to authenticate the packet before allowingthe packet to pass the same way that the redirecting host does.

IP Measurement Protocol (IPMP)

Introduction

The practice and need for active network measurement is wellestablished, however, current tools are not well suited to this task,mostly because the protocols which they employ have not been designedfor measurement of the modem Internet.

ICMP, for example, is widely used for measurement despite its well-knownlimitations for this task. These limitations include it being treateddifferently than other IP protocols at routers and hosts. ICMP has alsoreceived bad press from denial of service attacks and because of thenumber of sites generating monitoring traffic. As a consequence someISPs disable ICMP even though this potentially causes poor performanceand does not comply with RFC1009.

The protocol of the present invention operates as an echo protocolallowing packet loss, path length, route, RTT and in some cases, one-waydelay measurements to be taken. Packets are generated by a measurementhost and returned by an echoing router or host, known as an echoingsystem herein. The translation of router time stamps to real-time timestamps is supported through a separate information request and replyexchange between the measurement system and systems that insert timestamps into the echo request or reply.

Current packet probing techniques are not suited to measuring packetdelay at the router level. Routers often make bad measurement targetsbecause they are optimized for the relatively simple task of forwardingpackets. Routers may process tasks that are resource intensive andtherefore an opportunity for a denial of service attack at low priorityor not at all. Some measurement techniques construct measurement trafficthat can be difficult to efficiently detect and respond to amongst othernetwork traffic. This type of measurement traffic precludes measuring ofa router and makes the task of identifying where delay occurs in thenetwork difficult.

IPMP addresses these issues by providing a measurement protocol that istightly constrained, efficient and easy to implement. FIG. 6 shows anexemplary embodiment 60 of a process for employing packets sent usingthe Internet Measurement Protocol of the present invention for measuringperformance of particular links in a network. Each recipient of an IPMPpacket upon receiving an IPMP packet constructed by a measurement host,which IPMP packet includes instructions for a recipient of the IPMPpacket (element 61) examines a contents of the IPMP packet forinstructions for the recipient before forwarding the IPMP packet(element 62), and then processes the IPMP packet in accordance with theinstructions, if any (element 63).

The protocol has been designed so measurement packets can be processedwith about the same level of computation as IP packet forwarding. Theprotocol is intended to allow for easy implementation inhardware/firmware so as to provide for highly accurate measurements. Itshould be noted that only the TTL and Timestamp fields in the PathRecords are dynamic, all the other fields are likely to be the same forall the Path Records inserted at a particular stamping location.

The IPMP has a number of options to allow it to measure a number ofdifferent properties of the links and devices on a path between twoendpoints. It is intended that it should be practical to process IPMPpackets in the same forwarding path as normal (non-IPMP) packets withoutany (significant) performance impact. To achieve this it is anticipatedthat a device will pre-compute all but one or two of the components ofthe path record and insert some combination of these components based onthe options field of the packet.

The option fields of the IPMP request packet are defined with theobjective of allowing a forwarding device to determine what, if any,path records should be inserted with the minimum amount of logiccomplexity.

Remote Measurement

There are many applications of the IP Measurement Protocol where it issufficient to be able to perform measurements only on paths originatingwith the measurement host. However, there are also applications,protocols and users/operators that would be served by being able tomeasure the properties along paths that originate at hosts other thantheir own.

Some straightforward examples of such non-local measurement would be ISPoperators wishing to monitor their customer's link quality to be able todemonstrate they have provided an agreed upon level of service. Whilethe same customer may wish to have a third party organization performthe same monitoring to provide the customer with the same assurances,particularly if their traffic crosses multiple provider networks.

An example of an application/protocol use for non-local monitoring mightbe client copy multicast trees. The source of the multicast tree couldmeasure path properties not only between the source and the receiversbut also from receiver to receiver and reform the tree based on themeasured properties of the paths between the different receivers.

To avoid hosts having to run many different client/server processes foreach different entity that wishes to perform remote measurement, and toprovide a common security framework IPMP provides a mechanism to supporta remote measurement function.

To make it possible to perform measurements, from a remote location, ofpaths that do not start or end at that location, the IPMP provides amechanism for allowing redirection of the IPMP packet. This mechanismprovides hooks to support methods for authenticating IPMP packets toprevent the unauthorized use of the redirection function.

FIG. 7 shows an exemplary embodiment of a method 70 for performing aremote test of a link between a first remote network device and a secondremote network device by a measurement host. The measurement host beginsthe test by transmitting to a first remote network device an IPMP packetrequesting a measurement test of a link between the first remote networkdevice and a second remote network device (element 71). This request maybe in the form of a redirected echo request. The first remote networkdevice actually performs the desired test upon receiving the IPMPmeasurement test request packet (element 72) by sending an IPMPredirected echo request packet to the second remote network device fromthe first remote network device (element 73). Upon receiving the IPMPredirected echo request packet by the second remote network device,which IPMP echo redirected request packet includes instructions for arecipient of the IPMP redirected echo request packet, the second remotenetwork device creates an IPMP echo reply packet and includes relatedinformation in the IPMP echo reply packet based on the instructions inthe IPMP redirected echo request packet (element 74). Upon receiving theIPMP echo reply packet, the first remote network device processes theIPMP echo reply packet (element 75) and forwards information included inthe IPMP echo reply packet to the measurement host (element 76).

FIG. 8 shows another exemplary embodiment 80 of a method for performinga remote test of a link between two remote network devices from ameasurement host device. Upon receiving by a first remote network devicean IPMP packet, which includes an address of a measurement host deviceas a source address, an address of a first remote network device as adestination address, a flag indicating the IPMP packet is a redirectionrequest packet, and a predetermined field with an address of a secondremote network device as a redirection address to which the IPMP packetis to be redirected (element 81), the first remote network device beginsby relabeling the source address of the IPMP packet with the address ofthe first remote network device before forwarding the IPMP packet(element 82). In addition, the first remote network device relabels thedestination address of the IPMP packet with the address of the secondremote network device before forwarding the IPMP packet (element 83).The second network device begins by responding to the relabeled IPMPpacket by sending a reply IPMP packet to the first remote network deviceby exchanging the source address of the received IPMP packet and thedestination address of the received IPMP packet in the reply IPMP packet(element 84). Upon receiving the reply IPMP packet by the first remotenetwork device, the first remote network device re-labels a destinationaddress of the reply IPMP packet with the address of the measurementhost device before forwarding the reply IPMP packet to the measurementhost device (element 85).

Packet Formats

IPMP Echo Request and Echo Reply Packets

Optional Data Section Formats

Defined Data Section Types Type# Length Field? Name 0 No (L = 1) Pad 1Yes Error Return 2 Yes Identification Data (Measurement Host) 3 YesIdentification Data (Redirection Host) 4 No (L = 8) Original SenderAddress/Port 5 Yes Redirect Security Option 6 Yes Redirect Data 7 No (L= 12) Redirect Options 255 No (L = 1) End Original Sender Address/Port

Redirect Security Option

Redirect Options TTL: 1 byte DSCP: 1 byte Start TTL: 1 byte DestinationAddress: 4 bytes Destination Port: 2 bytes Options: 2 bytes

Error Return

Error Types Value Error 1 Bad Checksum 2 Missing Required Data Elements3 Security Option Required 4 Security Option Rejected IPMP Options

R = Record Path Record: 1 bit F = Fastpath ONLY Timestamps Requested: 1bit T = Timestamps Requested: 1 bit A = All Extra Info Requested: 1 bitS = Swap Faux Ports on Echo: 1 bit d = Data Section Present 1: bit t =Toggle Record Path on Echo: 1 bit r = Reverse Path TTL: 2 bits P =Packet Type: 3 bits Value Packet Type 000 Echo Request 001 Echo Reply010 Information Request 011 Information Reply 100 Redirected EchoRequest 101 Redirected Echo Reply 110 Echo Redirect Request 111 EchoRedirect Reply Reverse Path TTL Value New TTL 00 Unchanged 01  63 10 12711 255Record Path Record

If this field is 1 then a Path Record SHOULD be inserted by any devicethat forwards this packet. If the field is 0 then a device forwardingthe packet MUST NOT insert a Path Record into the packet. The echoinghost MAY insert a Path Record on reception or transmission of the packeteven if doing so would otherwise be prohibited by this option.

Fastpath ONLY Timestamp Requested

If this field is 1 then a Path Record SHOULD NOT be inserted unless itcan be done in the same processing path that would be taken by a regulardata packet. The objective of this option is to allow measurement to berestricted to those points where inserting the path record will notaffect the forwarding of the IPMP packet with respect to non-IPMPpackets. This may be of use if the IPMP packet is being insertedperiodically into a stream of packets so that the position of the IPMPpacket in the data stream is not disturbed.

Timestamp Requested

If this field is 1 then any Path Records inserted into the packet SHOULDinclude a timestamp in the path record. If this field is 0 then any PathRecords inserted into the packet SHOULD NOT contain a timestamp. Thisfield allows the IPMP packet to be used to perform a function similar totraceroute, without the need to collect timing data.

All Extra Info Requested

If this field is 1 then any Path Records inserted should contain anyoptional information elements that a device may choose to insert. Thisoption allows for elements to advertise any additional properties of thepath taken by the IPMP packet that they choose to make available.

Swap Faux Ports on Echo

If this field is 1 then the echoing host MUST swap the values in theFaux Src/Dst Port fields when returning the packet. This allows bothforward and backward paths of a flow to be measured by one packet. Theswapping of the ports is needed to insure that any packet filters act onthe packet as if it were part of the flow being measured.

Request/Reply

If this field is 0 then the IPMP packet is a Request packet, if thefield is 1 it is a Reply packet.

Toggle Record Bit on Echo

If this field is 1 then the echoing host MUST toggle the value of theRecord Path Record field when it receives the packet. This allows forpath records to be recorded in only one direction by turning on or offthe stamping process when the packet reaches the echoing host.

Path Record formats Without Timestamp

With Timestamp

Extensions Format

Defined Extension Types Type# Length Field? Name 0 No (L = 1) Pad 1 YesReference ID Extension 2 No (L = 13) IPv6 Address (partial) 3 Yes LinkSpeed (in kbps) 4 Yes Link MTU (in bytes) 6 No (L = 3) Queuing Type 7 No(L = 3) Congestion Control Type 255 No (L = 1) End Flags

Flag Fields TT = Timestamp Type 0 = Undefined 1 = Local source 2 =External (Stratum 2) source 3 = Reserved 4 = Reserved 5 = ~UTC 6 = UTC 7= No Timestamp F = Processed in “Fastpath” 0 No 1 Yes AT = Address Type0 = IP address of interface 1 = IP address of interface (non-responsive)2 = IP address of IPNP proxy + Reference ID 3 = Non-IP address L =Stamping Location 0 = Packet RX 1 = Packet TX 2 = Internal processing 3= Unspecified A = Accuracy 0-31, most accurate bit position intimestamp, compared to ‘real time clock’ on the device, this will be theworst of the number of bits of resolution of the device's clock and themaximum time difference between the real time clock at the time thepacket is stamped and the value of the timestamp placed in the packet. T= Tunnel (De/Enlcapsulation Point 0 = No 1 = Yes E = Extensions 0 = No 1= Yes R = Reserved Version = 0Faux Source Port, Faux Destination Port

In order for IPMP to be used to monitor the characteristics of the pathbeing taken by the data packets of an application it will be necessaryfor the IPMP packets to be filtered and queued in a manner identical tothat of user data packets. In order to allow such filtering to beperformed, in the location where the source and destination port fieldsof a TCP/UDP packet are located an IPMP packet contains two “faux” portfields, which allow it to be matched to any per flow filters that mightbe in use. The real source and destination port fields used by the IPMPpacket are found further down in the IPMP packet header.

The IPMP packet queue value, the IPMP packet source port queue value,and the IPMP packet destination port queue value allow an IPMPmeasurement packet to be queued or filtered based on a five-tuple ofvalues when combined with the IP source and destination addresses.

Faux P-Type (Packet Type)

For those devices with packet filters that include the packet type fieldof the IP header in determining how to process a packet, and are IPMPaware, this field SHOULD be used by the filter in place of the actualpacket type field, which will always contain the IPMP packet type.

Checksum

The checksum is the 16-bit one's complement of the one's complement sumof the IPMP packet message starting with the Faux Source Port. Forcomputing the checksum, the checksum is initialized to zero.

Path Pointer

The position, in bytes from the beginning of the IPMP packet, of thenext available path record location.

The Path Pointer MUST always point to a word (4 byte) aligned locationin the packet.

Length

The total length, in bytes, of the IPMP packet. The length should notnormally exceed 556 bytes. That is the data field plus the spaceallocated for path records should not exceed 544 bytes. Longer packetsrisk being discarded if they need to be forwarded over a path with anMTU less that 576. Within these limits a maximum of 45 path records maybe included in the packet, allowing 4 bytes for a unique identifier inthe data field.

Returned TTL

Zero in the echo request. The value of the IP header TTL field when thepacket was received by the echoing system in the echo reply.

Data

The data field is set by the measurement host. The echo reply containsan identical data field to the echo request. The content of the datafield must allow the echo reply to be matched with the echo request whenit arrives at the measurement host.

TTL

The value of the TTL field in the Path Record is set to the value of theTTL in the packet when transmitted by the device, which inserted thePath Record.

By comparing the TTL field of consecutive Path Records it can bedetermined if the time delta between two consecutive Path Recordsmeasures the time between two directly connected devices or if there areintermediate (non-IPMP aware) devices between the those that insertedthe Path Records.

Stamping Location

The Stamping Location field indications where in the device the PathRecord was inserted into the Echo Request packet.

If the field value is 0 then the Path Record was inserted at theinterface where the packet was received. If the field value is 1 thenthe Path Record was inserted at the interface where the packet wastransmitted. If the field value is 2 then the Path Record was insertedat an internal location in the device. If the field value is 3 then thePath Record was inserted at an unknown/unspecified location in thedevice.

Usage Example:

If host A sends an Echo Request to D with a TTL of 255 and both B and Cinsert Path Records, with TTLs of 254 and 253, then when the EchoRequest returns to A it can determine that there are no devices betweenB and C. But without knowing the stamping location it does not know whatwas measured. Suppose that B stamped at the ‘rx’ location and C stampedat the ‘rx’ location then the difference in the timestamps would be dueto the processing at B and the propagation delay of the B→C link, andany variation in the difference seen over repeated measurements would bedue entirely to variations in delay within B. However if C stamped at‘tx’ instead of ‘rx’ than any variation between measurements may becaused by either B or C or both. By marking the stamping location it ispossible to determine what was or was not measured by the difference intwo consecutive timestamps.

Address

If the value of the Address Type field is 0, the Address field MUSTcontain the address of the interface at which the packet was processedby the system that inserted the Path Record into the Echo Request orEcho Reply packet, as well as the address to which any InformationRequest packets should be sent to.

If the value of the Address Type field is 1, the Address field MUSTcontain the address of the interface at which the packet was processedby the system that inserted the Path Record into the Echo Request orEcho Reply packet. Unlike the case above, if the field value is 1 thesystem will NOT respond to Information Request packets at this address.

If the value of the Address Type field is 2, the Address field containsthe IP address of an IPMP packet ‘proxy’ which will reply to InformationRequest packets on behalf of the system, which inserted the Path Record.If the value of the Address Type field is 1 there MUST be a Reference IDfield in the Path Record. The value in the Reference ID field identifiesthe interface at which the packet was processed by the system thatinserted the Path Record. For any given ‘proxy’ address the value of aReference ID MUST uniquely identify an interface, but the same value MAYused by different proxy addresses to identify different interfaces.

This flag is designed to allow a system operator to support the IPMPwithout requiring the processing of Information Request packets by theinterfaces that inserted the Path Records. If the value of the AddressType field is 3, the Address field contains a non-IP address value, moreaccurately it contains a value which is not the IP address of theinterface, which inserted the Path Record, since it may be any 32 bitvalue it MAY by chance be an IP address of some other system. The valueof the Address field SHOULD be static while a system is up. The valueSHOULD be static across system restarts. The value is not guaranteed tobe globally unique, but SHOULD be unique at least amongst systemsbelonging to the same AS.

This value is designed to allow a system operator to support the IPMPwithout being required to expose the addresses of their systems to theprotocol while still providing a unique identifier to be associated withthe interface, which inserted the Path Record. If the value in theAddress field is not the IP address of the receiving interface or of anIPMP packet ‘proxy’ this value MUST be used. This value SHOULD also beused if the IP address of the interface is a ‘private’ address, e.g.10.0.0.1.

Timestamp

The time at which the Path Record is inserted into the packet isrecorded as a reduced size form of an RFC1305 NTP format timestamp. Therelationship between this timestamp and real time, if there is one, maybe derived using information from an IPMP Information Reply packet, orit may be inferred from a combination of the Fastpath, Timestamp Typeand Accuracy fields. This reduced size timestamp is designed to allowthe entire Path Record to fit into 3 words, or 4 words for Path Recordswith a Reference ID.

Timestamp Type

The Timestamp Type field gives an indication of the clock source thatthe timestamp was derived from. If the Timestamp Type is 0 then theclock source is of undefined quality and/or may be subject to arbitraryamounts of drift. An example case would be a PC router using the OSclock for the timestamp, in this case the software performing thestamping may have no knowledge of the quality of the clock source andthe value of the OS clock may be subject to large adjustments.

If the Timestamp Type is 1 then the clock source is a local oscillatorwhich may drift but which is not subject to adjustments. Differentstamping points on a device with a Type 1 source are neither guaranteedto have the same rate of drift nor to have identical values. If theTimestamp Type is 2 then the clock source is an external clock signal ofquality and is not subject to adjustments. Different stamping points ona device with a Type 2 source are not guaranteed to have identicalvalues, but they are guaranteed to have the same drift rate. If theTimestamp Type is 5 then the clock source is an external clock signal of(Stratum 1/GPS) quality (i.e., it does not drift because it IS thereference time), which is not subject to adjustments. Further thesecond's value in at least the 3 highest order bits of the timestamp,corresponding to bits 16-18 of an NTP timestamp, will have a value whichdiffers by no more than +/−2 from the value of bits 16-18 of an NTPtimestamp from a station at (+0 GMT). This allows the ‘missing’ upperbits to be determined if the receiver knows the correct value of realtime (+0 GMT). Different stamping points on a device with a Type 5source are not guaranteed to have identical values, but they areguaranteed to have the same (˜0) drift rate. If the Timestamp Type is 6then the device inserting the Path Record asserts that the value in theTimestamp IS the UTC time value for +0 GMT, within the accuracy asdefined by the Accuracy flag. Different stamping points on a device witha Type 6 source are guaranteed to have the same time value (+/−Accuracy)and the same (˜0) drift rate.

Fastpath

If the Fastpath field value is 1, aside from the alterations to contentsof the IPMP packet, the IPMP packet was processed and routed identicallyto a normal data packet containing the same IP header fields (addresses,ports, DSCP). This field allows the measurement host to determine howclose the reported times reflect the delays seen by regular datapackets.

Tunnel

If the Tunnel Encapsulation field is 1 then the device inserting thePath Record is a de/en-capsulation point for the packet. This may be anyform of encapsulation that will prevent the insertion of Path Recordsand results in transmission over equipment with variable delays. Forexample, IPSEC tunnels, MPLS encapsulation, IP-over-ATM, etc. The flagdeliberately does not indicate if the stamping device is the source orend point of a tunnel since unless all devices along the path are IPMPaware it might be possible to have two records the first indicating anencapsulation followed by one indicating a decapsulation making itappear that there was a tunnel between the two points, when in factthere was more than one tunnel between the two points.

IPMP Information Request and Information Reply Packets

Information Request

Info Flags

R = Reference ID Present If this flag is 1 then the information requestpacket contains a Reference ID. T = Timestamps Present If this flag is 1than the information request packet contains one or more Timestamps. E =Reference ID Extension Present If this flag is 1 then the informationrequest packet contains a Reference ID Extension. Information Reply

Real Time Reference Point

Version = 0.Flags

The Flags field indicates the presence of optional elements in theinformation request. The information reply MUST contain the same valuein the Flags field as the request packet contained.

Last

If there is a timestamp included in the information request the Lastfield indicates which is the last timestamp. If the Last field is 0 thenanother timestamp follows, if the Last field is any non-zero value thenthere are no more timestamps.

Checksum

The checksum is the 16-bit one's complement of the one's complement sumof the IPMP packet message starting with the version number. Forcomputing the checksum, the checksum and returned checksum fields arezero.

Precision Hi

The number of bits in the whole seconds part of timestamps that arevalid. A Precision Hi of N, means that the timestamps wrap around every2^N seconds.

Precision Lo

The number of bits in the fractional part of timestamps that are valid.

Length

The total length, in bytes, of the IPMP packet. The length should notnormally exceed 556 bytes. That is the Real Time Reference Points andPerformance Data fields should not exceed 524 bytes. Longer packets riskbeing discarded if they need to be fowarded of a path with a MTU lessthat 576. If no performance data is included 32 Time Reference Pointsmay be included in the packet. The IPMP packet MAY be the MTU sizesupported by the path, so equipment should be prepared to process IPMPpackets of this size.

Performance Data Pointer

The position, in bytes from the beginning of the IPMP packet, of theperformance data field if it exists. If there is no performance datathis field is 0.

Forwarding IP Address

The address of the interface to which the Information Request was sent.

Accuracy

The maximum difference between actual real time and the inferred realtime of any timestamp generated by this interface. If there is norelationship between real time and the timestamps recorded by theinterface or the extent of the difference from real time is unknownaccuracy is set to 0.

IPMP Packet Processing Overhead

The maximum difference between the time taken to process and forward anIPMP packet and the time taken to forward an IP packet with the samecharacteristics. If the overhead is unknown this is reported asMAX_TIME, i.e. all bits to 1.

Real Time Reference Point

A real time reference point gives the relationship between real time andthe timestamp that would have been placed in a Path Record by theinterface at that time. If there is no relationship between real timeand timestamps no reference points are included in the InformationReply.

If there were any timestamps present in the information request packetthen the reply packet SHOULD contain a real time reference pointcorresponding to each timestamp in the request packet. If the host doesnot believe that a valid reference point can be returned, for example ifthe host recently restarted and believes the timestamp was taken beforethe restart, it MAY return a reference point with a real time of 0, forthe reported timestamp.

Performance Data

The Performance Data field allows arbitrary information from the MIB ofthe system or the interface to optionally be included in the InformationReply. It is formatted as a VarBindList from the SNMPv2-PDU. In thiscontext ObjectSyntax is the only valid choice within VarBind.

I.E. IPMP-PERFORMANCE-DATA DEFINITIONS : := BEGIN IMPORTS ObjectName,ObjectSyntax, FROM SNMPv2-SMI; -- IPMP simplified list elementIPMPVarBind : := SEQUENCE { name ObjectName, value ObjectSyntax } --variable-binding list VarBindList : := SEQUENCE (SIZE (0 . .max-bindings)) OF IPMPVarBind ENDIP Protocol Header Values

-   Version=4-   IHL=5-   Identification=0-   Flags=DF-   Fragment offset=0-   IP Protocol type=TO BE ASSIGNED.-   IP options are forbidden.    Processing of IPMP Packets    Measurement Host Processing

Turning to FIG. 1, shown therein is an exemplary embodiment of a method10 for creating an IPMP packet according to one aspect of the presentinvention. A measurement host constructs an IPMP request packet (element11), encapsulates the IPMP request packet in an IP datagram and theappropriate link layer protocol (element 12) and sends the IPMP requestpacket into the network (element 13). Performance information is gleanedfrom the presence or absence of a reply, the delay between the requestpacket and the reply packet the value of TTL and the path record(s) ifpresent and possibly the presence of errors (element 17).

The measurement host, when constructing the echo request, MUST set allwords from the end of the data field to the end of the echo requestpacket (the space allocated for path records) to zero (element 11).

The data field SHOULD contain information that allows the measurementhost to match echo replies to echo requests. The data field might alsocontain checking information for part or all of the data and/or controlfields of the IPMP packet. This checking information SHOULD allowmatching of echo requests and replies.

When an IPMP echo reply packet arrives the checksum is recomputed(element 14). Unless further protection is provided in the data field anIPMP echo reply packet with an incorrect checksum SHOULD be discarded(element 16) because of the risk of data corruption causing incorrectmatching with the echo request, or the reporting of invalid measurementdata.

Redirecting Measurement Host

Turning to FIG. 2, shown therein is an exemplary embodiment 20 of amethod for performing a remote test of a first network device connectionto a second network device according to another aspect of the presentinvention. When a host receives a packet with the IPMP packet optionpacket type field of 6 (Echo Redirect Request), the host acts as aredirecting measurement host (element 21). The redirecting measurementhost performs the following functions (elements 22-29):

-   1) Check for the presence of a Redirect Options data section    (element 22).    -   a) If no redirect options section present, return packet to        original measurement host with an Error Return section with        error value 2 (Missing Required Data Elements) (element 23),        else go to 2)-   2) If host requires authenticated redirect requests (element 24) (if    not, go to 4), check for presence of Redirect Security Option data    section (element 25).    -   a) If no security option section present, return packet to        original measurement host with an Error Return section with        error value 3 (Security Option Required) (element 26)-   3) If security option present and required, verify security option    (element 27).    -   a) If verification fails, return packet to original measurement        host with an Error Return section with error value 4 (Security        Option Rejected) (element 28), else go to 4).-   4) Construct New IPMP Echo Request Packet (element 29).

Turning to FIG. 3, shown therein is an exemplary embodiment of a methodfor constructing a New IPMP Echo Request Packet according to anotheraspect of the present invention. The method proceeds as follows:

-   -   a) Copy fields from Redirect Options data section element of        original packet into header (element 31)    -   b) Insert (Redirection Host) Identification Data data section        element if needed (element 32)    -   c) Copy (Measurement Host) Identification Data data section        element if present in original packet into new packet (element        33)    -   d) Copy Src Address and Port from original packet into an        Original Sender data section element.    -   e) Set IPMP packet Options, Packet Type field to 4 (Redirected        Echo Request), zero remainder of packet, set Path Pointer and        compute IPMP packet checksum.

Turning to FIG. 4, shown therein is an exemplary embodiment 40 of amethod for processing a redirected echo reply according to yet anotheraspect of the present invention. When a host receives a packet with theIPMP packet option packet type field of 5 (Redirected Echo Reply), thehost acts as a redirecting measurement host (element 41). Theredirecting measurement host performs the following functions:

-   1) If host requires authenticated redirect requests (element 42),    check for presence of Redirect Security Option data section (element    43).    -   a) If no security option section present, zero out any path        records present and return packet to echo host with an Error        Return section with error value 3 (Security Option Required)        (element 44)-   2) Check for presence of Original Sender data section (element 45).    -   a) If no Original Sender data section present, return packet to        echo host with error value 2 (Missing Required Data Elements)        (element 46)-   3) If security option present and required, verify security option    (element 47).    -   a) If verification fails, return packet to echo host with an        Error Return section with error value 4 (Security Option        Rejected) (element 48)-   4) Copy Original Sender Address/Port to Destination Address and Port    fields of header (element 49 a).-   5) Set IPMP packet option Packet Type field to 7 (Echo Redirect    Reply) (element 49 b)-   6) Set IPMP packet option Record Path Record field to zero (0)    (element 49 c)-   7) Set TTL based on IPMP packet option Reverse Path TTL field    (element 49 d).    Echoing System Processing

The IPMP Echo Request packet and Echo Reply packet formats are designedto make processing at the stamping points simple and efficient, at theechoing point however there are a number more complex functions that anechoing system may have to perform.

Turning to FIG. 5, shown therein is an exemplary embodiment 50 of amethod for processing an IPMP Echo Request packet according to stillanother aspect of the present invention. On receipt of the IPMP EchoRequest (IPMP Option Packet Type=0 or 4) packet the echoing systemconstructs the echo reply packet from the echo request packet by(element 51):

-   1. exchanging the IP source and destination addresses (element 52)-   2. checking the IPMP packet checksum (element 53 a), if checksum    invalid, either add Error Return data section with value 1 (Bad    Checksum), may require moving any path records already present or    drop the packet (element 53 b).-   3. optionally inserting a path record (as described in section    3.3.1) (element 53 c).-   4. if the IPMP packet option Toggle Record Path is set to 1 (element    54), then toggle the value of the Record Path Record field of the    IPMP packet options (element 55).-   5. if the IPMP packet option Swap Faux Ports is set to 1 (element    56), then swap the values of the Faux Source/Destination Port fields    (element 57).-   6. if the Packet Type field is 0 (element 58 a), set it to 1    (element 58 b), if 4 (element 58 c), set it to 5 (element 58 d).-   7. set TTL according to Reverse Path TTL option (element 59 a).-   8. calculate the IPMP packet checksum (element 59 b).-   9. schedule the packet for forwarding taking account of the Faux    P-type field if appropriate (element 59 c).

Processing IPMP Information Request packets requires more resources thanan Echo Request. Direct measurements are not made from InformationRequest packets. Consequently an implementer may choose to processesInformation Request packets off the interface card and/or at lowpriority.

Forwarding System Processing

A forwarding router does not need to be IPMP aware. In the simplest casean IPMP packet is forwarded like any other IP protocol packet.

If the router forwards schedules packets based (perhaps in part) on thevalue of the IP protocol field, from the IP header, then the forwardingrouter must use the Faux P-type field of the IPMP packet header forscheduling instead of the IP protocol field. A forwarding router mayinclude a path record as described below.

Path Record

Inclusion of path records is optional. A path record MAY be inserted byforwarding routers (on the forward or reverse path) and the echoingsystem.

A system that adds a path record MUST increase the Path Pointer by thesize of the inserted path record, which must be a multiple of 4 bytes inlength and must also update the Checksum field. The length of the packetis not changed. Before inserting the path record the path pointer plusthe size of the path record MUST be compared with length to ensure thatsufficient space is available for the new path record.

A system that adds a path record MAY include a timestamp in the pathrecord using the timestamp NTP format. If it does not include atimestamp the timestamp field in the path record is left unaltered.

Denial of Service Attacks

Because IPMP echo request packets are processed with about the sameeffort as forwarding an IP packet they do not introduce any new denialof service opportunities.

IPMP Information Request packets require more processing and may be usedas the basis of a denial of service attack in the same way as anyinformation request on a router or host. Because Information Requestpackets are not used to make measurements an implementer may implementprotection against denial of service attacks made with these packets inthe same way as other information requests. This might involveprocessing IPMP Information Request packets at a low priority orregulating the maximum flow of packets. Since the IPMP InformationRequest packet is echoed by the responding interface it could be used asa reflector in a DOS attack by a host that sent packets with falsesource addresses. The use of a proxy host to respond to InformationRequest packets should make it possible to detect and stop such attacks.Also since the volume of legitimate IPMP Information Request packettraffic should be low, the proxy may simply limit how many requests itprocesses.

The use of the redirection function for a denial of service attack isaddressed in the Security Considerations section.

Discussion

Checksums

The IPMP packet checksum is calculated by the measurement host when itcreates the echo request packet. It is updated (as described in section4.2.1) by forwarding routers that insert a route record into the IPMPpacket. The checksum MUST be checked by the echoing host, and by theredirecting host (if any). Packets with bad IPMP packet checksum SHOULDbe discarded, but hosts MAY choose to return a Bad Checksum Error Returninstead.

Checksum Update at a Forwarding Router.

A forwarding router that does not include a path record does not checkor modify the IPMP packet checksum. (Normal IP forwarding occursincluding decrementing TTL and updating the IP header checksum.) Aforwarding router that includes a path pointer must update the IPMPpacket checksum. This MAY be done in two ways:

-   a) Absolute. Check that the checksum matches for the received    packet. If the checksum does not match, set the checksum in the    forwarded packet to 0. If the checksum in the received packet does    match add the Route Record to the packet and recalculate the    checksum.-   b) Relative. Form the checksum of the path record (this will be a    constant for a particular interface if timestamps are not used) and    the previous checksum. Option a) or b) is selected on the basis of    efficiency.

If possible option b) SHOULD be used as option a) allows for errors tobe introduced and then covered up.

Timestamps

The timestamp field is coded following the conventions described inRFC1305 NTP but using reduced number of bits.

NTP Timestamp Format

Summarizing from RFC1305:

In conformance with standard Internet practice, timestamps are specifiedas integer or fixed-point quantities, with bits numbered in big-endianfashion from 0 starting at the left, or high-order, position. Allquantities are unsigned and may occupy the full field width with animplied 0 preceding bit 0. Timestamps are represented as a 64-bitunsigned fixed-point number, in seconds relative to 0 h on 1 Jan. 1900.The integer part is in the first 32 bits and the fraction part in thelast 32 bits. In the fraction part, the non-significant low order can beset to 0.

This format allows convenient multiple-precision arithmetic andconversion to UDP/TIME representation (seconds), but does complicate theconversion to ICMP Timestamp message representation, which is inmilliseconds. The most future time that can be represented is 4,294,967(some time in the year 2036) with a precision of about 200 picoseconds,which should be adequate for even the most demanding measurements. RFC2030 (SNTP) contains a proposal for extending timestamps beyond the year2036.

IPMP Timestamp Format

The IPMP Timestamp Format includes bits [16:31] of the ‘seconds’ word ofan NTP timestamp and bits [0:23] of the ‘seconds fraction’ of an NTPtimestamp. This format reduces the overall size of the Path Records.This reduced timestamp should be sufficient for all purposes of the IPMPbeing accurate to about 50 nanoseconds, and taking 18 hours for theseconds field to wrap around. If archival time stamps are needed thenthe sending host can use IPMP info request messages, if needed, todetermine the values of the high order seconds bits.

Inferred Real Time

The real time of the timestamp may be inferred when a system provides anIPMP Information Reply packet with at least one Real Time ReferencePoint earlier and one later than the timestamp. For the purpose of thisinference the clock drift of the interfaces clock is assumed to belinear and linear interpolation is used between the two nearest RealTime Reference Points where one is greater than and one is less than,the timestamp. The accuracy field of an Information Reply reports thegreatest difference between an inferred real time, calculated usinglinear interpolation, and true real time.

Minimum Implementations.

Echoing System

The simplest echoing system implementation returns the IPMP echo requestpacket without a path record. As described in section 3.2 this onlyrequires that the IP source and destination addresses be exchanged, thetype field changed and the packet scheduled for forwarding. Because ofthe format of the IPMP echo request and echo reply packets this can beimplemented with a very small number of instructions. A system that doesnot insert path records does not need to processes IPMP Echo Requestpackets.

Systems which just provide this level of implementation allow a numberof measurements to be made that are not currently possible, particularlyif they are routers that processes ICMP at a low priority to avoid DOSattacks.

Forwarding System

Forwarding systems do not need to be IPMP aware.

A forwarding system that is IPMP aware may include path records withonly the Forwarding IP Address set. This requires writing the address tothe packet and updating the checksum and Path Pointer in the packet asdescribed in section 3.3.1 and 4.2.1. In this case the forwarding systemdoes not need to process IPMP Information Request packets.

Security Considerations

The IPMP echo redirect mechanism provides a method by which packets canbe directed to an arbitrary destination with a source address differentthan that of the host, which initially transmitted the packet. Such amechanism could be subverted to allow a distributed denial of service(DDOS) attack that could not easily be traced back to its source. The IPMeasurement Protocol provides a framework for authenticating packets sothat the redirection function can be made available to a restricted setof requesters. IPMP is designed so that even an implementation whichdoes not perform an authentication function on packets requestingredirection, while vulnerable to being used in a DDOS attack, insurethat the original source address of the attacker will be carried in theredirected IPMP packets.

Limiting of Unauthenticated Redirects

It is suggested that any implementation that allows the redirection ofunauthenticated echo request packets MUST limit the rate and/or numberof in flight packets either in general or on a per destination basis.Such limiting SHOULD become more restrictive if replies are not receivedfrom the echo host(s). By limiting unauthenticated echoes quickly andseverely if there is no response then the ability to use the IPMPredirect packet for DDOS attacks will be limited.

In addition it is suggested that any implementation that allowsunauthenticated redirects SHOULD only do so after validating that thesource address in the IPMP packet is not forged. This can be done in anumber of ways:

-   a. if the measurement host is on the same local network as the    redirection host, validation might be performed against the    redirection hosts arp table.-   b. in the case of ISP measurement, redirection might be restricted    to hosts from a private subnet, e.g. 10.1.X.X where there is router    filtering that prevents customer hosts or host outside the ISP from    sending packets with addresses in that subnet.

The above IP Measurement Protocol defines the processing tasks for arouter or other Internet device to permit direct measurement of thenetwork. As such, the processor in a router along with embedded softwarewill perform the necessary tasks set forth in the above IPMP packet.Thus upon receiving an IPMP compliant data packet, the router willprocess this data packet as set forth herein, and output the processeddata packet using known techniques but in accordance with thedescription herein. Other hardware implementations will be apparent tothose of skill in this art upon review of the IPMP set forth herein.

Turning to FIG. 9, shown therein is a method for using the Start Time toLive capability to enable or prevents measurements from being takenuntil the Time to Live (TTL) counter reaches a certain value, whichallows for measurement of very long paths or use of very short packets,in which it is not possible to fit all the measurement records into asingle measurement packet. The process 90 begins by creating an InternetProtocol Measurement Protocol (IPMP) packet by a measurement host(element 91). The IPMP packet includes in a predetermined field a starttime to live value and a time to live value (element 92). Themeasurement host encapsulates the IPMP packet in an IP datagram and apredetermined link layer protocol and sends the IPMP packet into thenetwork (element 93). Each recipient device decrements the start time tolive value (element 94). The start time to live value is then comparedto the time to live value and if equal (or less than) (element 95), therecipient decrements the time to live value (element 97). If not, theIPMP packet is forwarded to the next network device (element 96). Oncethe start time to live value reaches the time to live value, certainpredetermined actions will begin at the current recipient of the IPMPpacket and subsequent recipients (element 98).

Turning to FIG. 10, shown therein is an exemplary embodiment 100 of aprocess for using the IP Measurement Protocol to provide that a regulardata packet be replaced with an IPMP packet, which includes in one ofthe data sections extensions the data that would have been in theregular protocol packet, plus a flag that says “take this data out andprocess this data as if this data had been the only contents of anon-IPMP packet, where the faux ports and packet type were the realports and packet type.” As such, a router or other similar device thenprocesses the packet accordingly. The process begins by creating an IPMPpacket by a measurement host (element 101 ) and including predeterminedfield in the IPMP packet as a data packet (element 102). The measurementhost encapsulates the IPMP packet in an IP datagram and a predeterminedlink layer protocol and sends the IPMP packet into the network from themeasurement host (element 103). Upon receipt by a recipient networkdevice, the recipient identifies the packet as an IPMP packet andexamines a contents of the IPMP packet for instructions beforeforwarding the IPMP packet (element 104). If the address of therecipient device matches the destination address of the IPMP packet(element 105), the recipient network device processes a contents of apredetermined field of the IPMP packet as a data packet (element 106).If not, the recipient processes the IPMP packet as a measurement packet(element 107).

Turning to FIG. 11, shown therein is an exemplary embodiment 110 of amethod for creating an IPMP packet with a faux port. The measurementhost creates an IPMP packet (element 111). The measurement host includesin the IPMP packet instructions for a recipient of the IPMP packet,which instructions includes an instruction to a recipient to process theIPMP packet in accordance with an actual packet type and an actual portnumber included in a first and second predetermined location,respectively, rather than a faux packet type and a faux port number thatare included in the actual packet type and actual port number fields,respectively (element 112). The measurement host inserts in a packettype field in the IPMP packet an identification indicating the IPMPpacket is a faux packet type (element 113). The measurement host insertsin a port number field in the IPMP packet a faux port number, inserts ina first predetermined field in the IPMP packet an actual packet type,and inserts in a second predetermined field in the IPMP packet an actualport number (element 114). Finally, the measurement host encapsulatesthe IPMP packet in an IP datagram and a predetermined link layerprotocol and sends the IPMP packet into the network from the measurementhost (element 115).

References, which are hereby incorporated by reference herein:

-   [1] Braden, R., and J. Postel, “Requirements for Internet Gateways,”    STD 4, RFC 1009, USC/Information Sciences Institute, June 1987.-   [2] Mills, D., “Network Time Protocol (Version 3), Specification,    Implementation and analysis,” RFC 1305, March 1992.-   [3] Mills, D. “Simple Network Time Protocol (SNTP) Version 4 for    IPv4, IPv6 and OSI,” RFC 2030, October 1996.-   [4] Case, J., et al. “Protocol Operations for Version 2 of the    Simple Network Management Protocol (SNMPv2),” RFC 1905, October    1996.

Although various embodiments are specifically illustrated and describedherein, it will be appreciated that modifications and variations of theinvention are covered by the above teachings and are within the purviewof the appended claims without departing from the spirit and intendedscope of the invention. For example, certain versions of InternetProtocols (e.g., IPMP) are used in the above descriptions, butsubsequent versions, replacements, or other protocol performing the samemethods and techniques are within the scope of the inventions herein.Furthermore, these examples should not be interpreted to limit themodifications and variations of the invention covered by the claims butare merely illustrative of possible variations.

1. A method for performing a measurement in a network from a measurementhost comprising: receiving an Internet Protocol Measurement Protocol(IPMP) packet constructed by the measurement host, said IPMP packetincluding instructions for a recipient of the IPMP packet, saidinstructions including whether to include a time stamp or not in theIPMP packet when forwarding the IPMP packet; examining contents of theIPMP packet for instructions before forwarding the IPMP packet by thenetwork device; and processing the IPMP packet in accordance with theinstructions, wherein the time stamp occurs relative to an arrival ofthe IPMP packet at the recipient network device.
 2. The method accordingto claim 1, wherein said instructions include whether or not to includea path record when forwarding the IPMP packet.
 3. The method accordingto claim 1, wherein said instructions include authentication data. 4.The method according to claim 1, wherein said instructions includewhether or not to include additional information in the IPMP packet whenforwarding the IPMP packet.
 5. A method for performing a measurement ina network from a measurement host comprising: receiving an InternetProtocol Measurement (IPMP) Protocol packet constructed by themeasurement host, said IPMP packet including instructions for arecipient of the IPMP packet, said instructions including whether toinclude a path record or not in the IPMP packet when forwarding the IPMPpacket; examining contents of the IPMP packet for instructions beforeforwarding the IPMP packet by the network device; and processing theIPMP packet in accordance with the instructions, wherein the time stampoccurs relative to an arrival of the IPMP packet at the recipientnetwork device.
 6. The method according to claim 5, wherein saidinstructions include whether or not to include a time stamp whenforwarding the IPMP packet.
 7. The method according to claim 5, whereinsaid instructions include authentication data.
 8. The method accordingto claim 5, wherein said instructions include whether or not to includeadditional information in the IPMP packet when forwarding the IPMPpacket.
 9. An apparatus for performing a measurement in a networkcomprising: a processor to couple to the network; and a memory to storecomputer readable instructions causing a processor to: receive anInternet Protocol Measurement Protocol (IPMP) packet constructed by themeasurement host, said IPMP packet including instructions for arecipient of the IPMP packet, said instructions including whether toinclude a time stamp or not in the IPMP packet when forwarding the IPMPpacket; examine contents of the IPMP packet for instructions beforeforwarding the IPMP packet by the network device; and process the IPMPpacket in accordance with the instructions, wherein the time stampoccurs relative to an arrival of the IPMP packet at the recipientnetwork device.
 10. The apparatus according to claim 9, wherein saidinstructions include whether or not to include a path record whenforwarding the IPMP packet.
 11. The apparatus according to claim 9,wherein said instructions include authentication data.
 12. The apparatusaccording to claim 9, wherein said instructions include whether or notto include additional information in the IPMP packet when forwarding theIPMP packet.
 13. An apparatus for performing a measurement in a networkcomprising: a processor to couple to the network; and a memory to storecomputer readable instructions causing a processor to: receive anInternet Protocol Measurement (IPMP) Protocol packet constructed by themeasurement host, said IPMP packet including instructions for arecipient of the IPMP packet, said instructions including whether toinclude a path record or not in the IPMP packet when forwarding the IPMPpacket; examine contents of the IPMP packet for instructions beforeforwarding the IPMP packet by the network device; and process the IPMPpacket in accordance with the instructions, wherein the time stampoccurs relative to an arrival of the IPMP packet at the recipientnetwork device.
 14. The apparatus according to claim 13, wherein saidinstructions include whether or not to include a time stamp whenforwarding the IPMP packet.
 15. The apparatus according to claim 13,wherein said instructions include authentication data.
 16. The apparatusaccording to claim 13, wherein said instructions include whether or notto include additional information in the IPMP packet when forwarding theIPMP packet.
 17. A computer readable media having encoded thereoncomputer readable instructions causing a processor to: receive anInternet Protocol Measurement Protocol (IPMP) packet constructed by themeasurement host, said IPMP packet including instructions for arecipient of the IPMP packet, said instructions including whether toinclude a time stamp or not in the IPMP packet when forwarding the IPMPpacket; examine contents of the IPMP packet for instructions beforeforwarding the IPMP packet by the network device; and process the IPMPpacket in accordance with the instructions, wherein the time stampoccurs relative to an arrival of the IPMP packet at the recipientnetwork device.
 18. The computer readable media according to claim 17,wherein said instructions include whether or not to include a pathrecord when forwarding the IPMP packet.
 19. A computer readable mediahaving encoded thereon computer readable instructions causing aprocessor to: receive an Internet Protocol Measurement (IPMP) Protocolpacket constructed by the measurement host, said IPMP packet includinginstructions for a recipient of the IPMP packet, said instructionsincluding whether to include a path record or not in the IPMP packetwhen forwarding the IPMP packet; examine contents of the IPMP packet forinstructions before forwarding the IPMP packet by the network device;and process the IPMP packet in accordance with the instructions, whereinthe time stamp occurs relative to an arrival of the IPMP packet at therecipient network device.
 20. The computer readable media according toclaim 19, wherein said instructions include whether or not to include atime stamp when forwarding the IPMP packet.